The operation of airlines and airports today focuses on achieving maximum efficiency to keep operating costs as low as possible while continuing to provide travelers with a safe and economical mode of travel. It is desired to keep the time an aircraft spends on the ground at an airport between landing and takeoff, more specifically between arrival at and departure from the gate, to the minimum required to unload arriving passengers and cargo, service the aircraft, and load departing passengers and cargo. Minimizing the time an aircraft spends on the ground or is engaged in ground maneuvers not only reduces delays in airline flight schedules, but also increases the possibility that an airline can schedule additional flights, providing travelers with more options and improving airline profits. Increased airport ground traffic, however, may be accompanied by an increased risk of ground incidents involving aircraft, ground vehicles, and even passengers and ground personnel. Consequently, reducing aircraft ground time should not be at the expense of increased ground safety risks.
Multiple airlines conduct both pushback and landing operations for multiple aircraft virtually simultaneously. This strains not only the available towing and other ground operations equipment, but also the available ground personnel. Aircraft ground time can be increased significantly when tow bars, adapters, tugs, or ground crews are not available when needed at taxi-in or pushback. Neither the airline nor the flight crew has any control over this situation. Moreover, if an aircraft is damaged during taxi-in or pushback or causes damage to another aircraft in a congested ramp environment, and the damage is not detected prior to takeoff because the cockpit crew's attention was focused in the cockpit on checklists or other procedures or ground crew were busy elsewhere, aircraft safety could be compromised.
Ramp congestion caused by increasing numbers of flights, stringent aircraft scheduling requirements, and efforts to squeeze large jets into gates originally designed for much smaller aircraft contributes to traffic jams and reduced maneuvering space in the ramp area. Some studies have indicated that the location of most of the incidents resulting in damage that occur during aircraft ground travel happen at the ramp entry or exit area. At this location, taxi lines leading into and out of the gate area converge, and an aircraft is less likely to be in communication with air traffic or other controllers. Pilots and other flight crew are more likely at this point to be relying on an airline's ramp control procedure or ground crew input for guidance. The largest percentage of incidents in one study occurred within 20 feet of the nose wheel parking line, within the gate stop area, when the flight crew is typically relying entirely on ground crew guidance and signals from ground crew or elsewhere for clearance from obstacles and for final taxi instructions. Noise from operating aircraft engines may also interfere with communications between flight crew and ground personnel.
One study found that more incidents occur during aircraft arrival than during departure. One possible explanation for this is that there may be more obstacles for an aircraft to encounter when entering the congested area next to gates and terminal buildings. Another reason may be related to the large number of pushback, power-out, and power-turn procedures that are conducted during departure operations while incoming aircraft are trying to maneuver into gates or other parking areas. Damage to ground vehicles and other aircraft, especially where taxiing aircraft share a common maneuvering area, and injuries to people, mainly ground personnel but occasionally passengers, can also occur. The personal injuries notwithstanding, financial and other losses to an airline from such incidents are potentially substantial.
In addition to ramp collision incidents such as those described above, ground safety can be significantly compromised by the jet blast from an aircraft jet engine, as well as by the potential for engine ingestion when aircraft engines are kept in operation, even at idle speeds, within the ramp area. The addition of jet blast, also known as jet efflux, or engine ingestion created by an aircraft taxiing into a congested ramp area with one or more engines operating virtually guarantees that, at some time, something will be damaged or someone will be injured.
Jet blast data, measured from an aircraft's tail with the engines at low RPM settings, indicate that the damage profile can extend from the outboard wing-mounted engines to more than 200 feet beyond some larger aircraft. Within this area, jet engines can generate hurricane-level exhaust forces of almost 100 knots. Most of the reported jet blast damage incidents typically occur in the ramp area during pushback, powerback, taxi-out, or taxi-in. The position of the operating jet engines relative to gates, ground equipment, people, and other aircraft, especially smaller light aircraft, when breakaway power is applied can significantly influence the occurrence of jet blast or engine ingestion damage incidents. Because aircraft with engines powered while in the process of turning are frequently involved in such incidents, using powered engines to maneuver an aircraft without assistance from a tow vehicle is highly likely to compromise ramp and ground safety. The presence of a tow vehicle, however, is not likely to prevent damage if an aircraft's engines are running and the aircraft is in the process of making a sharp turn. Careful management of an engine-powered aircraft moving on the ground is required, particularly on congested ramps not designed for large aircraft. A pilot (and ground control) maneuvering an aircraft under such conditions must be aware of the potential jet blast and engine ingestion damage area when directing the ground movements of aircraft with operating engines. Ensuring safety is difficult under these circumstances.
Positioning a jet aircraft so that the engine forward thrust is directed away from gate areas, people, and ramp equipment and the jet blast is not directed into the gate area is helpful, but the direction of the jet blast can change as the aircraft is maneuvered into or out of the gate. This occurs, for example, during powerback operations, when the flight crew employs engine thrust reversers to direct thrust ahead of the aircraft to push the aircraft backward, changing the direction of the jet blast. Damage to other aircraft, especially small aircraft, ground vehicles, and personnel, remains a distinct possibility as long as an aircraft's engines are running. Suggestions for minimizing the hazards associated with jet blast and engine ingestion have helped somewhat, but both continue to present significant safety challenges in ground areas where an aircraft's engines are in operation during ground operations.
The pilot and cockpit crew are required by agencies that regulate air traffic to follow very specifically defined procedures during landing and takeoff, as well as during the period when an aircraft is travelling on the ground between landing and takeoff. These procedures are, by necessity, designed to ensure that aircraft landings, takeoffs, and ground maneuvers are as safe and efficient as possible. As noted above, increased airport ground congestion can present significant safety challenges to the pilot and cockpit crew during aircraft ground travel. Ideally, pilots must be aware of runway, taxiway, ramp, and gate environments at all times. Their awareness of these areas outside their aircraft must be especially focused, however, when there are other aircraft and ground vehicles present. Unfortunately, particularly following pushback, the pilot and other cockpit crew members are required to focus on checklists and activities internally within the cockpit related to pushback and engine start rather than the external environment. Consequently, the heads and eyes of the cockpit crew tend to be directed down into the cockpit as these tasks are performed, which can decrease their awareness of other vehicles and persons in the aircraft's immediate path of travel. Some of the safety issues discussed above could occur as a result.
Pilots must currently perform required sequences of procedures upon landing and taxi-in to a parking location and then upon pushback from the parking location, taxi-out, and takeoff. The sequences of these procedures are premised upon either the availability of a tow vehicle to move the aircraft on the ground when the engines are not operating or upon the operation of the engines to enable ground movement of the aircraft. The hazards of operating aircraft engines in a ramp or gate environment have been discussed above. Tugs present their own challenges to efficient aircraft ground movement. Neither situation enhances pilot efficiency or aircraft safety.
The movement of tugs generally contributes to ground vehicle traffic and congestion. Tugs also must be monitored to keep track of their locations so they may be moved to a required location by the time a tug is needed to pushback a departing aircraft. Although pilot controlled and remotely controlled tugs are disclosed in the art, for example in U.S. Pat. No. 6,928,363 to Sankrithi and U.S. Pat. No. 6,305,484 to Leblanc, respectively, such tugs are not widely available, and a ground crew team is still required to monitor and move tugs and to carry out the pushback process. The use of tow vehicles, moreover, increases the list of procedures a pilot must perform and monitor, as well as the time an aircraft is on the ground.
In addition, since the pilot and cockpit crew are focused on pushback procedures relating to movement of the air craft by the tug, the ground crew must ensure that no part of an aircraft structure will impact any fixed object or other aircraft or vehicle. The size of the ground crew required when an aircraft is moved into or out of the ramp or gate area by a tow vehicle typically increases over that required when an aircraft uses its engines for ground movement. Ground crew are also required to return tow vehicles from the location where they are detached from the aircraft to the gate area for reuse with another aircraft. This system is not a particularly efficient one.
A system and method for reducing turnaround time of an aircraft is described in U.S. Pat. No. 7,891,609 to Cox et al, owned in common with the present application. The system and method described therein suggests that aircraft turbines may be turned on only when needed and are turned off until takeoff or after landing. The aircraft is moved along taxiways using at least one self-propelled undercarriage wheel. This method focuses on reducing turnaround times by having all of the required equipment available for turnaround and departure and minimizing the use of motorized tugs while providing an enhanced communication system between the pilot and ground personnel. McCoskey et al, in U.S. Pat. No. 7,445,178, describes a powered nose aircraft wheel system useful in a method of taxiing an aircraft that can minimize the assistance needed from tugs and the aircraft engines. A precision guidance system is disclosed for controlling movement of the aircraft on the ground to minimize collision damage during taxi. Neither of the foregoing patents acknowledges or otherwise recognizes that pilot and/or cockpit efficiency or aircraft safety is affected by the systems described therein.
The prior art, therefore, does not disclose a method of improving or enhancing pilot efficiency and aircraft safety during aircraft ground travel or during aircraft ground travel in an aircraft driven independently on the ground by at least one powered self-propelled drive wheel.